As sparks continued to fly around the tinderbox of Bahrain, and as the troubled kingdom's Grand Prix drew ever closer, Crown Prince Salman bin Hamad bin Isa Al Khalifa refused to countenance cancelling the event.

Yesterday, amid initial rumours that they might head home, the Force India team did not run in the afternoon practice session, preferring to finish early and rebuild morale after the incident on Wednesday evening in which four team members were momentarily caught up in clashes between police and protesters and had a Molotov cocktail land close to their vehicle.

A Force India team van was also momentarily confronted by a burning tyre that was rolled in front of it.

The deputy team principal, Bob Fernley, said: "We are absolutely committed to racing here. What we are doing is a slight rescheduling to meet the requirements that we need to do – and that will take place. But we will be there for qualifying and for the race.

"We have had issues, as you all know, and we have to make sure that the crew are comfortable in the environment. But the crew are totally committed to delivering qualifying and the race – and if it means a limited or no FP2 [Friday second practice session] in order to achieve that, that is the decision we will have to take.

"We are doing the best we can to make sure the crew are safe. We have assurances and I don't believe there will be any issues. There will be protests and I think it was an unfortunate incident, but unfortunate incidents happen. When it is your team it happens to, you have to deal with it in a proper manner."

An independent poll published yesterday suggested that 77 per cent of the population were in favour of the race going ahead. Crown Prince Salman said: "I genuinely believe that the race is a force for good. All of the people are excited that you are here.

"I guarantee the problems faced by Force India were not directed at Formula One. Cancelling the race would encourage extremists."

Sauber also reported an incident on Thursday evening, when their minibus was approached by masked men as it had to slow down on the motorway. "The mechanics noticed fire on the median strip of the highway," said the team spokesman, Hanspeter Brack. "The traffic was slow, cars had their hazard flashers on. The team members saw a few masked people running over to their lane, where a bottle was burning as well. The minibus moved to the very right side of the highway and went past the situation."

Though no team personnel were injured in any of the incidents, they ratcheted up the tension as more demonstrations were held. The first was on the Zayyaq Highway, close to the Bahrain International Circuit, immediately after the second practice.

Others followed in the wealthy Saar suburb and Banijamrah later in the evening. Both are near the troubled Budaiya Road area in the north-west. The US Embassy leaked information on no-go areas, which include the area to the left of Hamad Road on the route back from the circuit towards Manama, the area to the east by Sanad and Sitra which have previously seen trouble, and the north-west area by Sanabis, not far from the old Pearl Roundabout and the opulent Ritz Carlton Hotel, where a fourth demonstration was held in the vicinity of Karranah and Abu Saiba.

A fifth demonstration is planned near the University of Bahrain, much closer to the Formula One circuit, at 4pm tomorrow, right in the middle of the race.

The Bahraini government has imposed a curfew on the waterways around the kingdom between 6pm and 4am. "Of course we fear most the possibility of some sort of track invasion on Sunday during the race, or some sort of protest on the grid prior to the start," said Crown Prince Salman, who is also chief executive of Bahrain International Circuit, on Thursday evening. "But we have tried to be subtle in our security."

But McLaren's Martin Whitmarsh said: "The calendar has been set for some time and we are competitors, so we are here to race. There is a lot of support in all parts of society, but often the majority are not heard on these occasions."

Crown Prince Salman said: "Protests will happen, it's part of the political process in any country. But there's a very big difference between protesting and rioting."

Yesterday the action on the race-track was of secondary importance. Lewis Hamilton headed the first session for McLaren and the Shanghai winner, Nico Rosberg, led the second for Mercedes.